170 GEO. S. HUNTINGTON 
in a sufficient number of individuals of each type in the series, 
we might conceivably arrive at the following results: 
1. In the more primitive types the peripheral pulmonary 
area X is supplied in a large portion of the individuals by bronchus 
A, in a much smaller number by bronchus B. 
2. The intermediate group of genera shows a decided numer- 
ical preponderance of bronchus B. A few individuals still carry 
bronchus A, and a still smaller number have developed bronchus 
C, either alone or in combination with B. 
3. Finally in a third group, comprising the most recent and 
advanced forms, bronchus C has become dominant. There are 
relatively few B bronchi, and an A bronchus is only occasionally 
found. 
Then, and only then, could we speak of a phylogenetic magra- 
tion which has carried bronchus A from its original point of 
origin on the ventro-lateral primary bronchus through the angle- 
site B to its final position C on the stembronchus. 
In the first of the above hypothetical groups, with bronchus A 
dominant, bronchus B appears as a progressive phyletic variant. 
In group 2, with B the prevalent bronchus, A is an archeal rever- 
sional, C a progressive phylogenetic variant. In group 3, both 
A and B are reversions, the former of the progonal, the latter of 
the ataval type. Even then the term ‘migration’ is to be inter- 
preted only figuratively. 
It is true that for the purpose of rapid examination of a series 
of bronchial trees, the concept and the term expressing the same 
are convenient and compact, and that they readily indicate the 
cardinal differences observed in the comparison of divergent 
types. Further, used in the sense above stated, they convey 
concisely certain broad evolutionary facts. Speaking phylo- 
genetically it might be not altogether objectionable to refer to a 
bronchus as ‘migrating’ or ‘wandering’ from its original location 
to a new site in comparing a more archeal type of bronchial tree 
with one further advanced in progressive evolution. I have so 
used the term in my earlier publication. But it should be 
employed, if at all, with a clear definition of its meaning, not, as 
Narath has done, as designating an actual shift occurring during 
the ontogeny of the individual form. 
